Remove git from README

This repo is now supposed to focus on LaTeX
and its compilation via Docker etc. alone.
Bringing git into the equation was always confusing.

The git content moved to

https://collaborating.tuhh.de/m21/public/wiki/-/wikis/Version-Control
5 jobs for master in 4 minutes and 35 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  .Pre
passed #510779
preflight

00:00:09

 
  Build
passed #510781
README.pdf

00:00:47

passed #510780
tex

00:03:41

 
  Test
failed #510783
test-pdfs

00:00:42

passed #510782
test-self

00:01:00

 
Name Stage Failure
failed
test-pdfs Test
E       assert 100000 <= 56917

tests/test_pdfs.py:120: AssertionError
=========================== short test summary info ============================
FAILED tests/test_pdfs.py::test_file_size[README.pdf] - assert 100000 <= 56917
=================== 1 failed, 13 passed, 2 skipped in 2.34s ====================
make: *** [Makefile:34: test-pdfs] Error 1
Cleaning up file based variables
ERROR: Job failed: exit code 1